Magnetic stepping mechanism,especially for the feeding movements of grinding machines



March 25, 1969 R. BLOHM 3,434,361

MAGNETIC STEPPING MECHANISM, ESPECIALLY FOR THE V FEEDING MOVEMENTS OF GRINDING MACHINES Filed Jan. so. 19e? @0M INVENTO United States Patent O 3,434,361 MAGNETIC STEPPING MECHANISM, ESPECIALLY FOR THE FEEDIN G MOVEMENTS OF GRINDING MACHINES Robert Blohm, Kampchaussee 59/ 63, Hamburg 80, Germany Filed Jan. 30, 1967, Ser. No. 612,708 Claims priority, application ,iGrmanL Feb. 10, 1966, B 85 5 Int. C1. F16h 27/02 U.S. Cl. 74--142 5 Claims ABSTRACT F THE DISCLOSURE BACKGROUND OF THE INVENTION Field of invenlion The invention relates to a magnetic stepping mechanism, especially to generate extremely small and extremely exact feeding movements in grinding machines.

In order to achieve the necessary accuracies in connection with very high requirements to be met by the surface quality of the Workpieces to fbe processed, it is necessary for the automatic downfeed in long-table type horizontal surface grinding machines to be effected in possibly uniform individual downfeed movements true to scale. These individual downfeed movements, due to the requirements to be met by the surface quality, may in certain cases amount to only /ooo mm. per grinding step.

In the case of surface grinding machines with a completely hydraulic drive, these downfeeds are effected hydromechanically by means of hydraulically operated lock pawl stepping mechanisms.

Description of the prior art Modern machine tools employ electrical devices in a considerable extent. As a result of this, also horizontal surface grinding machines mostly employ electromagnet couplings to effect the downfeed. When employing electroma-gnetic couplings, mechanically exact values are easily changed due to the pulse dependent switching operations and, because of the inaccuracies caused thereby, it is possible, in particular with the last finishing cut, that the downfeed is too great which may lead to the workpiece being rejected.

To effect the automatic downfeed on long-table type horizontal surface grinding machines, reduction gears have a-lso been employed already in connection with hydromechanic stepping mechanisms or magnetic couplings, whereby relatively great stepping motions were possible, said motions being reduced by means of the gearings. Such reduction gearings, however, constitute additional and costly special equipment which do not remove the inaccuracies of the stepping motions but only reduce them in proportion to their reduction ratios.

Moreovier, in the case of a hyidromechanical feed, a second hydraulic pumlp is necessary in order to prevent the table speed from being impaired during the downfeed operation. If only one single hydraulic pump were employed, such an impairment of the table speed would have an especially unfavourable result insofar as at the 3,434,361 Patented Mar. 25, 1969 ICC moment the downfeed movement is performed, the table would be in the process of reversal and the table drive would need the full output for the actuation of the table.

Therefore, it is the object of the present invention to provide a stepping mechanism for the feeding movement which is simple in construction and suited to perform extremely exact movements.

Summary of the invention In accordance with the invention, this object is obtained in that with a stepping mechanism in which the stepping movement is transferred by means of a stepping pawl adapted to be engaged in the toothing of a stepping wheel, the actuation of the stepping pawl is effected by an electromagnet controlled lby means of a control device. In a suitable further development of the invention, said stepping paWl is arranged on a pawl carrier rotatably supported at the axis of rotation of the stepping wheel, said pawl carrier being connected with the iron core of the electromagnet. Likewise, in a further development of the invention, the pawl carrier may also be a doublearmed pivotal lever, the one lever arm of which is connected with a manually operable releasing device, While the other lever arm carrying the stepping pawl has pivotally connected thereto the iron core of the magnet, possibly with the interiposition of a connecting linkage, and a return spring. In accordance with an especially important feature of the invention, the stepping pawl may be provided with a guiding edge cooperating with a stationary leading surface, which, for instance, may be arranged `at the machine frame, the tang of the stepping pawl engaging within the toothing of the stepping wheel or being disengaged therefrom in dependence upon the position of the stepping pawl guiding edge with respect to the leading surface.

The subject matter of the invention involves an electromagnetically operated stepping mechanism which may receive its pulses through an electronic control device. With such apparatuses it is possible to regulate via potentiometers, e.g. 1-20 downfeed movements per grinding pass. The magnetic stepping mechanism may be effective on a worm shaft which transfers the downfeed movement via a Worm wheel to the adjusting drive for the height adjustment of the workpiece holder or the grinding spindle of a grinding machine.

The actuation of the stepping mechanism in accordance with the invention is effected at the moment the table is reversed. In this operation, the magnet may perform one or several strokes for the actuation of the stepping mechanism so that the downfeed is effected by the amount of one or more tooth pitches of the stepping wheel. In accordance with the invention, the stepping mechanism is provided with a pulling pawl but without a locking pawl. Due to the arrangement of a gui-ding edge at the stepping pawl in cooperation with the stationary leading surface, the stepping pawl when in the position of rest is disengaged from the toothing of the stepping wheel, so that the height spindle may be adjusted ad libitum in both directions either manually or mechanically.

The invention will be described in more detail in the following by way of an example of embodiment shown in the accompanying drawings, without being restricted to the embodiment shown.

Brief description of the drawing FIG. 1 shows the stepping mechanism according to the invention in the position of rest and 'with the stepping pawl disengaged,

FIG. 2 shows the same stepping mechanism as FIG. l, however, at the end of the switching operation with the stepping Wheel.

Description of the preferred embodiment The stepping mechanism in accordance with the invention essentially consists of the stepping wheel 10 with the toothing 11, the stepping pawl 14 arranged n the pawl carrier 13, and the iron core 18 of the electromagnet 16 pivoted to the pawl carrier via the linkage 19. The stepping wheel is mounted on the shaft 12 connected with an adjustment drive for height adjustment, for instance a worm drive. The pawl carrier 13 is likewise supported on the shaft 12 of the stepping wheel 10, but rotatably, so that the pawl carrier may be pivoted about its point of rotation independently of of stepping movements of the stepping wheel. The pawl carrier 13 is designed as a swinging lever and consists of the two lever arms 22, 23 and lever arm 23r extending on the inner end of the arm 22 essentially straight-line beyond the point `of rotation which is formed by the axis of rotation of the stepping wheel 10. The manually operable release device 24 may act upon the end of the lever arm 23 of the pawl carrier via an actuation rod 25 supported in a corresponding guide 26. The lever arm 22 of the pawl carrier 13 pivotally supports thereon by means of the pivot pin 15, the stepping pawl. The actuacting linkage 19 connected with the iron core 18 of the lifting magnet, 16, and a return spring 21 are acting substantially at the end of the lever arm 22 and spaced from said stepping pawl. The linkage 19 is pivotally connected with the lever arm 22 by means of a bolt 20. Adjacent the stepping pawl 14, there is disposed an abutment member 29 with a stationary leading surface 30. A guiding edge 28 of the stepping pawl 14 cooperates with said leading surface 30 the edge 28 being arranged on a shoulder of the pawl formed at the side of the pivot pin opposite the tang 27. A spring is arranged between the stepping pawl 14 and the pawl carrier 13 s`o that the pawl is pressed into engagement with the stepping wheel 10.

In the illustration shown in FIG. l, the tang 27 of the stepping pawl 14 is disengaged from the toothing 11 of the stepping wheel 10. With the pawl in this position, the height drive may be adjusted in both directions by means of a manual wheel, or a fine-adjustment screw, not shown. The stepping pawl 14, during this operation, is retained in the disengaged position thereof by means of the engagement `of the guiding edge 28 and the stationary guiding surface 30 of the abutment member 29. The stepping of the pawl stepping mechanism in accordance with the invention may be effected either by means of the manually operated releasing device 24 or the electromagnet 16. In case `of manual operation, the releasing device 24 is pressed down, whereby the transfer lrod 25 is acting on the end of the lever arm 23 of the pawl carrier, and the pawl carrier is pivoted about the shaft 12 of the stepping wheel 10.

In this operation the guiding edge 28 slides Ialong the upwardly receding leading surface 30 of the -abutment member 29, and the tang 27 of the stepping pawl 14 engages with the toothing 11 of the stepping wheel 10, so that when the downward pressure on the releasing device 24 continues, and with the counterclockwise pivotal movement of the pawl carrier caused thereby, a stepping moment of the stepping wheel 10 will take place. With complete depression of the releasing means, for instance, the stepping distance X (FIG. 2) may be equal to the amount of tooth pitch of the stepping wheel 10. As soon as the releasing means 24 is released, the return spring 21 pivotally connected with the lever arm 22 of the pawl carrier 13 will retract the Ipawl carrier into its starting position, the tang 27 being lifted from the toothing 11 of the stepping wheel 10 by the cooperation of the guiding edge 28 of the stepping pawl :and the leading surface 30 of the abutment member 29, and retained in the disengaged position.

In case of elastomagnetic operation of the stepping mechanism, the feeding is effected principally in the same manner. The coil 17 of the electromagnet 16 is loaded by pulsed controlled by an electronic apparatus whereby the iron core 18 is pulled into the magnet. In this operation, the pawl carrier 13 is pivoted as described about the stepping wheel shaft 12 into the horizontal plane, and the stepping pawl 14 has its tang 27 engaging within the toothing 11 of the stepping wheel after the pivoting of the stepping pawl about its pivot pin 15 has been effected in dependence upon the cooperation of the guiding edge 28 with the leading surface 30 of the abutment member 29.

In the case of magnetic actuation, the stepping movement may be limited by means of the adjusting screw 31 arranged at the housing surrounding the magnetic coil, the end face portion 32 of the iron core getting into cooperation with the adjusting screw. This screw is especially suited for fine adjustment.

After interruption of the loading of the coil 17 of the electromagnet 16 with pulses, the magnet will drop, and the pawl carrier is turned back to its starting position according to FIG. l about the stepping wheel shaft 12 by means of the return spring 21 which may be pivotally connected with the bolt 20 of the lever arm 22 of the pawl carrier 12, taking along the iron core 18, the lifting of the pawl from the toothing of the stepping wheel being effected by the guiding edge 28 of the stepping pawl guided along the leading surface 30 of the abutment member 29.

What I claim is:

1. An intermittent rotary stepping mechanism comprising, in combination, a drive shaft rotatable about an axis, a toothed stepping wheel fixed upon said drive shaft, an oscillatable lever having a pivot substantially aligned with said axis, a pawl pivotally mounted on said lever having a tang for selective engagement with the teeth of said wheel and a cam engaging surface, a spring interposed between said lever and said pawl biasing said pawl tang toward engagement with the Wheel teeth and a fixed cam disposed adjacent said pawl having a cam surface defined thereon obliquely related to the path of movement of the pivot of said pawl adapted to be engaged by said pawl cam engaging surface during a predetermined portion of the oscillation of said lever releasing the engagement of said tang with the wheel teeth and thereby regulating the degree of indexing of said wheel with respect to the degree of oscillation of said lever.

2. A stepping mechanism as in claim 1 wherein said pawl includes first and second ends disposed on opposite sides of the pawl pivot, said tang being defined at said first end and said cam engaging surface being defined at said second end.

3. In a stepping mechanism as in claim 1, manual means connected to said lever for oscillating said lever.

4. In a stepping mechanism as in claim 1, an electromagnetic coil, -a movable core within said coil, and linkage? means connecting said core with said lever whereby energization of said coil oscillates said lever.

5. In a stepping mechanism as in claim 4, manual means connected to said lever for selectively oscillating said lever.

References Cited UNITED STATES PATENTS 768,667 8/1904 Kray 310-23 2,957,966 10/1960 Bennett 335-123 2,900,840 8/ l959 Greve 74-142 FRED C. MATT ERN, IR., Primary Examiner.

W. S. RATLIFF, JR., Assistant Examiner. 

